The present invention relates to a method of canceling noise in a communication system and a device therefor, which can reliably eliminate noise superposed on a transmitting signal during signal transmission.
Signals received through a transmission line are in many cases polluted by noise introduced during signal transmission, and thus it is necessary to remove a noise component in the received signals. Conventionally, such a noise component is removed by using a noise filter or by performing a suitable calculation matched to noise characteristics. For example, in telephone lines, an echo cancel process is carried out in accordance with the estimated characteristics of an echo path; as for measurement signals, calculation is performed in accordance with a moving average method, a frequency domain method, an integrating average method, or the like. However, if the frequency range of the transmitting signal overlaps with that of the noise or the waveform of the transmitting signal is similar to that of the noise, it is difficult to remove the noise by using a noise filter or by performing a calculation.
In view of this, the applicant of the present invention has proposed a method of canceling a noise component from a sensor output signal by processing both the signals from a sensor and an impedance element connected in parallel therewith, during signal transmission (Japanese Patent Application No. 63-68291). With this proposed method, however, since the amplitude of noise applied to the output transmission system of the sensor differs from that applied to the output transmission system of the impedance element, amplitude adjustment is essential to compensate for the amplitude difference.